1. Field of the Invention
This invention relates to cages for cylindrical roller bearings and, more particularly, to improved cages provided with a plurality of roller retaining devices fabricated of plastic material which are movable in circumferential direction, thereby enabling ready fabrication and assembly of the cages into roller bearings.
2. Description of the Prior Art
Generally, pressed, integral cages for roller bearings of the type in which either one of the bearing rings are separable, have encountered problems of limited dimensional accuracy in molding the teeth and lips projecting between adjacent rollers. Also, there is limited dimensional accuracy when bending and crimping the teeth during sub-assembly. Because of these dimensional inaccuracies, a tooth may excessively contact the roller or rollers, thereby impairing smooth rotation. Contrariwise, the extent of contact with related roller(s) by a tooth may be so insufficient as to result in much sinkage of the roller, thereby making assembly of a mating bearing ring very difficult.
In view of these drawbacks, various bearing cages of the so-called "separated" type have been developed, in which a bearing cage comprises a cage member and a discrete roller retaining device. An example of such a cage is shown in Japanese Utility Model Publication No. 7904/62, in which an auxiliary ring, namely, a roller retainer formed with a retainer groove having a width slightly smaller than the diameter of the pockets defined in a cage member, is inserted in the cage member. Another "separated" bearing cage is shown in Japanese Patent Publication No. 9608/63 in which a plastic retaining piece or pieces are heat bonded on both a radial inner face and an outer face or, alternatively, on either one of the above-mentioned two faces such that the retaining pieces of lips extend through a marginal part of the openings formed in the cage member.
The first "separate" type bearing cage discussed above still suffers from certain drawbacks. For example, since in its assembly a flange of the auxiliary ring is engaged with the axial end face or faces and, then, a post or posts, formed between the retaining groove, are press fitted to either the radial inner side or the outer side of the cage member, positioning of related elements is very difficult. In addition, since the post or posts in the retaining groove are supported against the flange, as a mere one-side support, when either an inner ring or an outer ring is not coupled during its assembly, the post is liable to be deformed by the weight of rollers. Even after the assembly is completed, the auxiliary ring may slip out from the cage member, during running, due to vibration or some other cause.
The second type of roller retaining device discussed above also has disadvantages. Because the plastic roller retaining member is heat bonded to the cage member, a great degree of skill is required in circumferentially positioning the teeth or lips exactly to each retaining hole or opening.
In addition to the aforesaid devices, integrally molded plastic cages have been used, but they are still unsatisfactory with regard to both strength and accuracy for high load appliances.
It is, also noteworthy that in both of the "separate" type of cages mentioned above, the roller retaining device or member is not allowed to take any relative displacement with respect to the cage member. Because of this, it has been found that some part of the cage restrains the rollers and is liable to impair bearing characteristics.
So far as the present inventors know, it is believed that the above-mentioned publications are the most relevant to the present invention. Attention is directed, also, to British Patent Specification No. 1215466. However, it is unclear whether the British patent teaches a construction allowing displacement of the roller retaining device relative to the cage member, which is deemed to have some drawbacks, particularly, similar to that of the first prior art device discussed above.
Accordingly, an object of the present invention is to provide a "separate" type bearing cage of high strength and high accuracy for a cylindrical roller bearing comprising a pressed or machined metal cage member and a roller retaining member which is fabricated from a plastic material.
Another object of the present invention is to provide a bearing cage, of various modifications, for cylindrical roller bearings which can be readily assembled without requiring any particular accuracy in the circumferential positioning between the cage member and the roller retaining device or member.
A further object of the invention is to provide bearing cages with various modifications which can be manufactured at low cost by virtue of the shaping of component parts by simplified steps. A still further object of the present invention is to provide cages especially suitable for cylindrical roller bearings capable of withstanding high service loads.